Floor-to-ceiling windows are highly desirable in today's real estate market, which is why many new office buildings in D.C. are mostly clad in flat panes of glass. "In many 'taut' glass buildings in D.C., architects have resorted to putting superfluous armatures on the exterior," Prince-Ramus says. "They build a taut glass facade and give depth by adding architectural features, like striations and leading lines. That's just not who we are."

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Working with the engineering firm Front, Rex designed a glass-clad building called 2050 M Street that looks nothing like its monolithic brethren. The curtain wall is composed of subtly curved windows that make the structure appear to melt into the downtown D.C. cityscape. Cleverly, it also adds floor space.

'Draconian' design standards
Designing anything beyond a basic glass box in D.C. is difficult. A rigid zoning law mandates that buildings top out at no more than 130 feet—about 12 stories tall. "The word I would use is 'draconian,'" says Joshua Prince-Ramus, principal of the New York–based architecture firm Rex, of D.C. building codes.

Because real estate in Washington is at such a premium, developers tend to build structures to the maximum allowable area. "The urban environment of D.C. is like Berlin or Paris because it feels like a superblock. Even if an architect changes a building's materiality, they're constructed to the property line. There has been a recent tension between heavy masonry buildings from the Neo-Federalist, Beaux Arts, and Brutalist eras and new taut, glass-skinned buildings. The two don't really have any dialog."

Transparency adds floor space
One of the design challenges was finding a way to give the building as much transparency possible. In most buildings, windows are supported by mullions—vertical strips that hold the glass in place, which impede sight lines. Prince-Ramus and his team were thinking about ways to support the windows with as few visual obstructions as possible while also giving the glass depth. Cladding the building in curved glass solved both the structural and aesthetic considerations. The gentle arc of each five-foot-wide glass pane is based on a circle with a 9.5-foot radius.

"It's a modest curvature but when you see it at the front, it has a dramatic effect on how it catches the light and reflects the environment, but it does it without any unpleasant distortion," Prince-Ramus says.

The curve makes the material stronger—just as corrugating metal gives it more stiffness—and eliminates the need for thick mullions. The panes are supported at their top and base where they meet each floor. To further the facade's glassy look, the architects made sure that the floors were extra thin where they approached the building's perimeter and accomplished this by tapering the ceiling depth.

Curving the glass also added more floor space to the 450,000-square-foot, 11-story building. Edges of the curves are considered to be "architectural features" and can, per code, extend four inches past the buildable lot area every five feet, which happens to be the width of each pane.

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Artful inspiration
Achieving the right reflectivity was another challenge since the glass needs to be coated for protection and energy efficiency. The architects looked to the work of minimalist artist Dan Graham to inspire the glass's look. "Graham's [glass] sculptures can be transparent when they're viewed obliquely, they're not reflective like a mirror—they're ethereal," Prince-Ramus says. "You never know what's in front of or behind you and that was the benchmark we were trying to achieve."

Economies of scale
Curved glass is typically expensive to fabricate but since the facade uses the same sized module throughout, economies of scale helped keep glass prices down. In addition to cost effectiveness, the repetition and reflectivity articulates the facade in unexpected ways as you walk past the building. Moreover, the developer is buying the material rather than going through a sub-contractor to help rein in costs.

To offset the building's slick appearance, the designers used lots of warm, natural materials inside. The lobby is clad in teak—the same wood you'd find on a yacht's deck—and the walls are covered in natural cowhide, a byproduct of the meat industry that would otherwise go to waste. "The hide patterning is reminiscent of a the style of book-matched stone that high-modernists like Mies and Gordon Bunschaft used in their lobbies," Prince-Ramus says. It was a way of using a sustainable material that was warm, but also has an honesty to a high-modernist aesthetic."

At the project's outset, the architects aspired to create a building that "aesthetically reconciles" architecture in D.C. By pushing the structure's design through engineering they were able to create something that's thoroughly modern and forward-looking, yet complements the cityscape.